1. Field of the Invention
This invention relates to a method and means of controlling the absorption of solar energy by a liquid contained in a greenhouse by means of varying the breakup and solar exposure of the liquid by linearly deforming, spraying or atomizing it in application to mass production and harvesting algae, desalination of water and extraction of carbon dioxide from flue gas.
2. The Current Needs
The worldwide discussion of the need for a practicable means of offsetting global warming by reducing emission of carbon dioxide has focused attention on sequestering the significant quantities of carbon dioxide released from coal fired power plants as the primary means of offsetting global warming. Considerable effort is currently underway, or under consideration, to develop methods of separating the carbon dioxide from the other constituents of the combustion flue gas. Its separation and collection requires its liquefaction for transportation or storage. One of the methods being studied, for sequestering the large quantities of CO2 that would be collected, is to transport it to sites suitable for deep-earth drilling and long-term storage in known underground cavities using deep earth drilling. It is recognized to be a costly solution, however.
An alternative solution is to utilize the CO2 by its absorption in the natural process of growing algae with sunlight. This method is currently under development in various stages ranging from laboratory studies and pilot scale tests to algae growing farms. The latter stage involves the use of large capacity growth beds, covering many acres, fed by sources of naturally growing algae culture plus nutrient-enriched solutions. These are blanketed with carbon dioxide enriched air under transparent canopies exposed to sun light. The growth rate of the algae is subject to the naturally varying conditions of sunlight and heat, as well as the varying and limited depth-penetration, into the nutrient solution, of the solar rays and carbon dioxide.
Methods currently used to offset the growth limiting factors involve solution stirring, including paddlewheel mixing, and bubbling of the air-CO2 mixture up through transparent (glass) columns of algae solution. The growth also requires alternating periods of darkness and light exposure. Improved means of controlling the several variables that effect growth can serve to increase process efficiency and cost-effectiveness.
The prevalence of micro-algae growth in coastal sea waters has adversely affected the economies of marine industries, e.g., the destruction of clam beds by “brown tides.” A low cost method of collecting, concentrating and harvesting the algae can overcome the problem.
The increasing shortages of water in developing countries point to the need of sources of desalinated sea water. Current methods of producing potable water by distillation or osmosis are costly in terms of both capital and operating expense. A low cost method that includes solar energy evaporation and condensate collection can provide a world-wide benefit. Investigations have been undertaken of the feasibility of absorbing carbon dioxide from flue gas into aqueous mixtures of reactive chemicals. Considerable interest has been shown in its well known reaction with magnesium hydroxide slurry to form the carbonates. By subsequently heating the reaction-product mixture, concentrated carbon dioxide is evolved and collected.
The magnesium hydroxide slurry is then recycled for reuse. A proposed means of employing this reaction in flue gas cleaning has involved the use of a conventional wet scrubber for the absorption, followed by circulating the slurry to a steam heated reaction vessel to drive off the CO2, Major questions pursuant to its industry adoption include the reaction time required for absorption and the energy required to extract the CO2.